Lubricating oil composition containing polyalkylene imine salicylate salts



United States Patent LUBRICATING OIL COMPOSITION CONTAINHNG POLYALKYLENE IMINE SALICYLATE SALTS Henricus G. P. van der Voort, Amsterdam, Netherlands,

assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware No Drawing. Filed May 27, 1965, Ser. No. 459,437

Claims. (Cl. 252-34) This patent application is a continuation-in-part of copending patent application, Serial No. 850,089, filed November 2, 1959, and now abandoned.

The invention relates to new and novel lubricating oil compositions having excellent detergent and wear-inhibiting properties.

Combustion engines, such as gasoline engines and diesel engines, are more or less subject to wear of cylinders, pistons and piston rings. In automobile engines, in particular, it is a known phenomenon that considerably increased wear occurs when the cylinder temperature remains relatively low, as is the case when driving short distances. According to the general view, this is due to moisture condensing on the cool cylinder walls in the presence of acids, such as sulfuric acid from sulfurous fuel, hydrohalic acids from lead scavengers, and organic acids from incompletely burnt gasoline. The corrosion caused by these acids, also termed cold corrosion, is responsible for much of the piston and cylinder wear in automobiles.

In order to inhibit wear in combustion engines, it has already been proposed to incorporate in the lubricating oil certain additives capable of rendering the said acids harmless by neutralizing them. Examples are oil-soluble neutral or basic organic metal compounds, such as calcium, barium or zinc salts of petroleum sulfonic acids, of alkylated hydroxy benzoic acids, and others. In many cases, it has been possible to obtain good results by incorporating such organic metal salts in the lubricating oil.

The use of metal salts, however, is attended by drawbacks. One disadvantage, for example is the fact that the metal salts formed by neutralization of the acids resulting from the combustion are generally insoluble in oil. This may lead to disturbances, particularly as a result of the formation of deposits in the combustion space which may subsequently cause precombustion.

To avoid the use of ash forming metal salts, simple amine salts of aliphatic carboxylic acids have been used, but such salts are utilized primarily as corrosion inhibitors and pour point depressants and lack detergent and wear inhibiting properties.

It has now been found that excellent detergency and wear-inhibiting properties can be imparted to mineral lubricating oil compositions by incorporating therein a minor amount of from about 0.5% to about 5% perferably from 1% to 3% by weight of a partially neutralized salt of a polyalkylene imine selected from the group consisting of polyethylene imine and polypropylene imine and mixtures thereof, in the molecular weight range of from about 2x10 to about 2x10 preferably from 5.3X to l.6 10 (light scattering method), and a monoor di-C alkyl salicylic acid and mixtures thereof, and preferably a mixture of monoand di-C alkyl salicylic acid. By partially neutralized salts of the present invention is meant that from 50% to 70% of the available nitrogen atoms of the polyalkylene imine re- 3,267,034 Patented August 16, 1966 main as free amino nitrogen atoms and the remainder are neutralized 'by the acid to form the alkyl salicylate salt.

The polyethylene and/or polypropylene imines used to form the salts of the present invention are obtained by polymerizing ethylene imine and/or propylene imine by well known means such as in the presence of an acid catalyst, e.g., hydrochloric acid or boron trifluoride, to form a high molecular weight polymer in the molecular weight range indicated above. The polymerization of ethylene imine and/ or propylene imine to high molecular weight ranges indicated above can be also accomplished by polymerizing these monomers in the presence of ammonia and elevated pressures, or by thermal decarboxylation of 2-oxazolidones. Specifically, methods for forming these polymers are described in US. Patents 2,182,306 and 2,318,730. Polyethylene imine in the molecular weight range of 3 x10 to 6 X10 is preferred for forming the partial amine salts with monoor di-C alkyl salicylic acids.

The alkyl salicylic acids used to form the salts of the present invention include mono-and/or di-C alkyl salicylic acids which may be prepared, for example, by alkylating phenol by means of olefins obtained in cracking petroleum fractions and then converting the corresponding sodium phenolates into alkyl salicylates (and alkyl phenols) by treating them with carbon dioxide according to the Kolbe-Schmitt reaction. In addition to alkyl salicylic acids, the corresponding alkyl phenols are obtained therefrom by acidification which may or may not be removed from the product.

The polyethylene imine and/or polypropylene imine having a molecular weight range indicated are reacted with alkyl salicylic acids to form partial salts of the present invention, preferably in the liquid phase in a homogeneous medium. These polyalkylene imines are generally employed in an organic solvent which, if desired, may also contain water. Suitable solvents are in particular alcohols having from 1 to 4 carbon atoms, e.g., methanol, ethanol, isopropanol and the butanols, as well as mixtures thereof with water and/or hydrocarbons. The hydrocarbons are, for example, gasoline fractions or benzenoid hydrocarbons. The alkyl salicylic acids are preferably also used as a solution in an organic solvent. Suitable solvents for this purpose are hydrocarbons, e.g., gasoline fractions or aromatic hydrocarbons, such as benzene, toluene, the xylenes, and the like.

In an advantageous embodiment of the invention an aqueous methanol solution of a high molecular weight (36 10 polyethylene imine is contacted with a solution of one or more alkyl salicylic acids in benzene, after which the solvents are removed by distillation, if desired, under reduced pressure. It should be observed that both the conversion and the separation of the final product are effected in a particularly simple manner. Especially as compared with the above-mentioned preparation of metal salts of alkyl salicylic acids, it is an important advantage that no operations, such as filtering or centrifuging, are required, since in this case it is only necessary to remove solvents, and this may be done by distillation.

The salt formation reaction is generally carried out at temperatures in the range of from 20 C. to C., although higher or lower temperatures are also possible. The reactants are generally reacted in such quantities that an excess of polyethylene imine is used so that from 50% to 70% of nitrogen atoms in the polyethylene imine remain free and the remainder are neutralized by the acid to form salts.

The products obtained are oil-soluble partial salts of polyalkylene imines in a high molecular weight range and alkyl salicylic acids. It has been found that lubricants in which these products are incorporated have excellent detergent and wear-inhibiting properties. This applies in particular to the inhibition of the wear of pistons, piston rings and cylinders which occurs in motor cylinders, e.g., in combustion engines, such as automobile engines, diesel engines and aero piston engines.

The high molecular weight oil-soluble partial polyethylene imine and/or polypropylene imine C alkyl salicylic acid salts are suit-able as additives to lubricants of various types. In the first place may be mentioned mineral lubricating oils of diverse viscosity, although the products are also suitably incorporated into synthetic lubricating oils as well as lubricating oils containing fatty oils. The products may also be worked up in lubricating greases.

The product obtained according to the invention may be added as such to the lubricant. In an advantageous embodiment the product is only partly freed from the solvents; a small quantity of a lubricating oil is then added and the remnants of the solvents are finally distilled oif, preferably diluted with a lubricating oil/or worked up into a lubricating grease.

The following examples illustrate the invention.

Example I A mixture of monoand di-C alkyl salicylic acids was prepared by alkylating phenol with C1448 olefins obtained in cracking petroleum fractions and then carboxylated to the corresponding sodium phenolates with carbon dioxide according to the Kolbe-Schmitt reaction to acidify the product. The resultant mixture (in xylene) contained 0.94 m.eq. COOH per gram.

The crude xylene-C alkyl salicylic acid mixture (306 parts) was diluted with benzene to approximately 1500 parts by volume, and about 35 .9 parts by Weight of polyethylene imine (M.W.=5 10 dissolved in 500 parts by volume of methanol, was added to the solution at room temperature. Part of the solvent was then removed by heating over a steam bath at atmospheric pressure, after which about 1500 parts by volume of a Venezuelan mineral lubricating oil (viscosity: 114 cs. at 100 F.) was added and the remainder of the solvent distilled off in a high vacuum (e.g., 0.3 mm. Hg) at 75 C. A clear concentrate, about 1433 parts by weight, was obtained, which concentrate was still clear after six months and was a partial polyethylene imine salt of C1448 alkyl salicylic acid about 30-50% neutralized.

Example 11 The procedure of Example I was followed using polypropylene imine (M.W.=5.3 X

1 part by weight of the concentrate of Example I was diluted with 7 parts by weight of the above-mentioned lubricating oil for the engine tests. The lubricating oil thus prepared was used in the engine tests given below.

Engine tests.Engine tests carried out in CPR gasoline engine with the doped lubricating oil which contained 1.4% by weight of polyethylene imine salt of the said alkyl salicylic acids of Example I, referred to in Table I as Composition A, showed a considerable reduction in ring wear and in the tot-a1 wear.

The fuel used was a motor gasoline which has a sulfur content of 0.06% and contained 0.7 ml. TEL per US. gallon. The temperature of the cooling water was 40 C. The figures in the following table show the wear in mg. of iron in experiments of 45 hours. The ring wear relates to all four piston rings.

l Average of two experiments, respectively, before and after the test with the new additive.

In the above engine tests, the substitution of simple polyalkylene imine salts of low molecular weight 500) such as N-tallow trimethylene diamine C1448 alkyl salicylate, or tetraethylene pentamine C1448 alkyl salicylate, for Example I polymeric salt of the present invention in the same amount as in Composition A, such compositions produced no desired benefits in wear reduction over that of neat oil.

The polymeric salts of the present invention may also be combined with other additives, such as anti-oxidants, detergent dopes, viscosity-index improvers, corrosion inhibitors, anti-foaming agents, pour point depressants, extreme-pressure and oiliness agents and other oil additives generally added to lubricants.

I claim as my invention:

1. A mineral lubricating oil composition consisting essentially of a major amount of mineral lubricating oil and from about 1% to about 3% of an oil-soluble partial salt of a polyalkylene imine selected from the group consisting of polyethylene imine, polypropylene imine, and mixtures thereof, having a molecular weight in the range of 2x10 to 2x10 and a C alkyl salicylic acid wherein from 50%-70% of the nitrogen atoms in the molecule remain as free amino nitrogen.

2. A mineral lubricating oil composition consisting essentially of a major amount of mineral lubricating oil and from about 1% to about 3% of an oil-soluble partial salt of polyethylene imine having a molecular weight in the range of 2x10 to 2x10 and a C alkyl salicylic acid wherein from 50%-70% of the nitrogen atoms in the molecule remain as free amino nitrogen.

3. A mineral lubricating oil composition consisting essentially of a major amount of mineral lubricating oil and from about 1% to about 3% of an oil-soluble partial salt of polypropylene imine having a molecular weight in the range of 2x10 to 2X10 and a C alkyl salicylic acid wherein from 50%-70% of the nitrogen atoms in the molecule remain as free amino nitrogen.

4. A mineral lubricating oil composition consisting essentially of a major amount of mineral lubricating oil and from about 1% to about 3% of an oil-soluble partial salt of polyethylene imine having a molecular weight in the range of 3x10 to 6x10 and a C1448 alkyl salicylic acid wherein from 50%-70% of the nitrogen atoms in the molecule remain as free amino nitrogen.

S. A mineral lubricating oil composition consisting essentially of a major amount of mineral lubricating oil and from about 1% to about 3% of an oil-soluble partial salt of polypropylene imine having a molecular weight in the range of 3x10 to 6x10 and a C1448 alkyl salicylic acid wherein from 50%-70% of the nitrogen atoms in the molecule remain as free amino nitrogen.

References Cited by the Examiner UNITED STATES PATENTS 2,736,658 2/1956 Pfohl et a1. 252--34 X 2,798,045 7/1957 Buck et a1. 25234 X 2,920,040 1/ 1960 Jolly 25234 X FOREIGN PATENTS 797,452 7/ 1958 Great Britain.

DANIEL E. WYMAN, Primary Examiner.

C. F. DEES, Assistant Examiner. 

1. A MINERAL LURICATING OIL COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR AMOUNT OF MINERAL LURBICATING OIL AND FROM ABOUT 1% TO ABOUT 3% OF AN OIL-SOLUBLE PARTIAL SALT OF A POLYALKYLENE IMINE SELECTED FROM THE GROUP CONSISTING OF POLYETHYLENE IMINE, POLYPROPYLENE IMINE, AND MIXTURES THEREOF, HAVING A MOLECULAR WEIGHT IN THE RANGE OF 2X10**4 TO 2X10**10 AND A C8-20 ALKYL SALICYLIC ACID WHEREIN FROM 50%-70% OF THE NITROGEN ATOMS IN THE MOLECULE REMAIN AS FREE AMINO NITROGEN. 